Hand truck step climbing mechanism



p 1953 s. B. WESSIC HAND TRUCK STEP CLIMBING MECHANISM 2 Sheets-Sheet 1 Filed Oct. 7, 1949 Iuvsuron,

I vlm M w. M a w R r a 8 P 1953 I s. B. WESSIC 2,653,672

' HAND TRUCK STEP CLIMBING MECHANISM Filed Oct. 7, 1949 2 Sheefs-Sheet 2 19v Mam I flTTORNEY.

latentecl Sept. 2 9

UNITED STATES PATENT oFFicE 3 Claims.

This invention relates to hand truck step climbing mechanism, the primary object of which is to provide a device which will lift a hand truck and its load step by step up a flight of steps.

A further important object of the invention is to provide a hand truck step climbing device which can be used on steps of varying sizes without adjustment.

A still further object of the invention is to provide a hand truck step climbing device which will accomplish the above objects in a more facile, economical and efiicient manner than has heretfore been employed.

Further important objects and advantages of the invention will become apparent to those skilled in the art from the following description of one particular form of the invention as illustrated in the accompanying drawings, in which:

Fig. l is a view in rear elevation of a hand truck equipped with mechanism embodying the invention;

Fig. 2 is a View in section on the line 2--2 in Fig. l; and

Fig. 3 is a view in section on the line 3-3 in Fig. 1.

handle l3 integrally connecting the side rails at their top ends, a bottom plate l4 fixed at right angles to the bottom ends of the rails II and I2,

and cross-pieces l5 connecting said rails intermediate their ends.

fixed to the bottom surfaces of the rails H and 2 respectively near their upper ends.

A rectangular plate ii is fixed to the bottom surfaces of the rails II and 52 near their lower ends and inverted U-shaped wheel brackets I8 and [9 are fixed on opposite lateral end portions of the bottom surface of said plate I! to extend downwardly therefrom. Both of these wheel brackets is and it are substantially identical, the left-hand wheel bracket 18 consisting of side plates 2% and 2| connected by a top web 22 and the right-hand wheel bracket I9 consisting of side plates 23 and 2 1 connected by a top web 25. Wheels 26 and 21 are revolubly mounted on the pins 28 and 29 respectively, which are carried by the wheel brackets I8 and I5 respectively in horizontal axial alignment.

A horizontal shaft 30 is revolubly mounted in bearings 3! and 32 carried by the bracket plates 2! and 23 respectively spaced rearwardly and up- V-shaped feet 56 and 57 are wardly from the axis of the pins 23 and 28, to have its axis of rotation parallel to the axis of the wheels 26 and 21.

An electric motor 33 to drive the shaft is fixed to the bottom surface of the plate I! in such a manner that its drive shaft 3 5, has its axis parallel to the axis of the shaft to. In order to utilize a small motor of relatively high speed, it is necessary to interpose a gear reduction device between the motor and the shaft and this device may assume di erent designs. Herein, the device is illustrated somewhat diagrammatically by a pinion gear fixed on said drive shaft 34 to be in constant mesh with a larger spur gear 36 fixed on the shaft 30. Referring to Fig. 3, the motor 33 is designed to rotate the drive shaft 34 and the pinion gear 35 in a clockwise direction and thereby to drive the spur gear 36 and the shaft 3!} in a counterclockwise direction.

Lift arms 31 and 38 of equal lengths are fixed on the shaft 39 adjacent the bearings 3| and 32 respectively. Referring again to Fig. 3, due to the counterclockwise rotation of the shaft 30 the arms 31 and 33 will revolve in a counterclockwise direction. In other words the outer ends of the arms 31 and 38 will be moving forwardly when rotating under the shaft 38, moving upwardly when rotating in front of the shaft 323, moving rearwardly when rotating above the shaft 3! and moving downwardly when rotating to the rear of the shaft 30. As shown in Figs. 2 and 3 the operating arm 3'! has a concave arcuate leading edge 39, a convex trailing edge il), and a bifurcated end portion 4| extending forwardly of the edge 39 in the direction of rotation of the arm 37. The arm 38 is identical with the arm 3?. Both arms 37 and 38 have identical rollers 42 and 23 respectively revolubly mounted in their respective end portions on a common axis of rotation which is parallel to the axis of the shaft 30.

An electric cable it enters the side rail ll near the handle l3, passes through a switch (not shown) which is located inside of the rail H and is controlled by the lever 47 which extends outwardly from the under side of rail H, down through the rail I l to a hole 48 located just above the plate I7, out through the hole 48, and from the hole 48 directly to the electric motor 33. The outer end of the power line 46 is connected to an electrical power outlet (not shown) when the step climbing mechanism is to be used.

To use the step climbing device, the opera atmg arms 31 and 38 are positioned preferably forwardly of the shaft 30, and the truck Hi is backed up to the steps to he climbed with the wheels 25 and 21 abutting the vertical face 49 of the first step to he climbed. The operator takes a position on the steps facing the truck l and grasping the handle l3 to exert an inward pull thereon. In this position the frame of the truck I0 will be at some such angle as indicated in Figs. 2 and 3.

The operator then actuates the electric motor 33 by movement of the switch lever 41 and the operating arms 31 and 38 revolve around and downwardly into contact with the tread 5| of the first step. When the rollers 42 and 43 contact the tread 5| their movement is arrested and continued rotation of the shaft 30 causes said shaft 30 to revolve bodily upwardly in an are around the axis of the rollers 42 and 43 to move the wheels 26 and 21 onto the tread 5| of the first step. When the wheels 26 and 21 have cleared the lip 52 of the tread 5| the inward pull exerted by the operator on the handle l3 will pull the rollers 42 and 43 and the wheels 25 and 21 inwardly to place the wheels 2'6 and 21 in abutment with the riser 53 of the next higher step. The rollers 42 and 43 will move forwardly to allow the wheels 26 and 21 to settle down on the tread 5|, and then be swung around forwardly, upwardly, and downwardly into contact with the tread 5 4 of the next higher step where the lifting procedure will be repeated. The same action will be repeated on each successive step until the entire flight has been climbed. In Figs. 2 and 3 the roller 42 is shown in contact with the tread 54 of the second step after the truck has climbed onto the first step.

Referring to Figs. 2 and 3,, when the truck in is in step climbing position the axis of the shaft 30 is approximately the same distance from the horizontal surface 5| upon which the wheels 26 and 21 are resting as the distance which the tread '54 of the step which the mechanism is designed to climb is from said surface 5|. It should be noted that the effective lifting lengths of the arms 31 and 38 are determined by the distance between the axis of the shaft 30 and the axis of the rollers 42. and 43 plus the radius of said. rollers 42 and. 43 in relation to the radius of the wheels 28 and 21. If the effective length is less than the distance which the axis of the shaft 30 is spaced above the surface 5| by the wheels, the arms 31 and 38 will not completely lift the wheels 26 and 21 onto the tread 54, while if the effective length is greater than the distance which the axis of the shaft 30 is spaced-from said surface 5|, the truck land its load will be lifted to a greater height than necessary to lift the wheels 26 and 21 to the next higher step and power will be wasted. In order to permit some variation in the angle at which thetruck. frame is disposed relative to the surface. 5|, it is desirable that when the frame is disposed at its preferred angle relativeto. the tread. 5| that. the axis of the, shaft 30 be substantially vertically above the axis of the wheels 26 and. 2].

In order that the path of the arms31. and. 38 shall be clear so that thearms can revolve continuously a full360 degrees aroundthe shaft 30, the axis of said shaft must be spaced from the plate [1 a distance greater than the effective form of the leading edges of the operating arms 31 and 38 is an important feature of this device in that it permits the arms 31 and 38 to reach over the lip of a step at a higher elevation than that of the shaft 30 without contact or hanging up of the intermediate portion of the arms 31 and 38 on the lip. This feature insures that the truck will not be pushed forwardly on its tread while being lifted.

While I have herein shown and described my invention in the one best form as now known to me, it is to be understood that structural variations may be employed without departing from the spirit of my invention, and therefore I do not desire to be limited to that precise form beyond the limitations which may be imposed by the following claims.

I claim:

1. A step climbing hand truck comprising in combination a substantially rectangular frame; a plate fixed to the bottom surface of said frame near its forward end; a pair of inverted U-shaped wheel brackets fixed to opposite lateral ends of said plate; wheels revolubly mounted in each of said wheel brackets, each of said wheels being revoluble about a common axis of rotation; a revoluble shaft journaled in bearings carried by said wheel brackets with its axis parallel to the axis of said wheels; a pair of spaced apart lifting arms fixed on said shaft; a motor fixed on said plate; driving means between said motor and said shaft; said motor being designed to rotate said shaft through said means in a direction such that the operating arms will revolve downwardly when to the rear of the shaft.

2. A step climbing hand truck comprising in combination a substantially rectangular frame; a plate fixed to the bottom surface of said frame near its forward end; a pair of inverted U-shape wheel brackets fixed to opposite lateral ends of said plate; wheels revolubly mounted in each of said wheel brackets, each of said wheels being revoluble about a common axis of rotation; a revoluble shaft journaled in bearings carried by said wheel brackets with its axis parallel to the axis of said wheels; a pair of spaced apart lifting arms fixed on said shaft; a motor fixed on said plate; driving means between said motor and said shaft; said motor being designed to rotate said shaft through said means in a direction such that the operating arms will revolve downwardly when to the rear of the shaft; each of said operating arms having an arcuate concave leading edge and a bifurcated end portion extending forwardly of said leading edge in the direction of rotation of said arm; rollers revolubly mounted in each of said bifurcated end portions, each of said rollers having a common axis which is parallel to the axis of said shaft.

3. A step climbing hand truck comprising in combination a substantially rectangular frame; a plate fixed to the bottom surface of said frame near its forward end; a pair of inverted U-shapedv wheel brackets fixedto opposite lateral ends of said plate; wheels revolubly mounted in each of said wheel brackets, each of said wheels being revoluble about a common axis of rotation; a, revoluble shaft journaled in bearings carried by. said wheel brackets with its axis parallel to the axis of said wheels; a pair of spaced apart lifting arms fixed on said shaft; a motor fixed on, said plate; driving means between said motor,

and said shaft; said motor being designed to rotate said shaft through said means in a direc tion such that the operating arms will revolve downwardly when to the rear of the shaft; each of said operating arms having an arcuate concave leading edge and a bifurcated end portion extending forwardly of said leading edge in the direction of rotation of said arm; rollers revolubly mounted in each of said bifurcated end portions, each of said rollers having a common axis which is parallel to the axis of said shaft; said shaft being spaced from said plate a distance greater than the combined distance between the axis of the shaft and the axis of the rollers plus the radius of the rollers; said shaft being arranged relative to the wheels so that when the truck is in stair climbing position the axis of the shaft will be substantially vertically above the axis of the Wheels; and the over-all length of the arms including the distance between the axis of the shaft and the axis of the rollers plus the radius of the rollers being substantially equal to the distance between the axis of the shaft and the surface upon which the wheels are resting when the truck is in operating position.

SYLVES'I'ER B. WESSIC.

References Cited in the file of this patent UNITED STATES PATENTS 10 Number Name Date 255,693 Tauber Mar. 28, 1882 1,191,394 Brown et al. July18, 1916 1,551,127 Whyel Aug. 25, 1925 2,400,824 Jackson May 21, 1946 15 2,506,292 B'oltson May 2, 1950 FOREIGN PATENTS Number Country Date 187,291 Germany June 24, 1907 20 577,797 Germany July 13, 1932 

